Nurses hit the picket line starting at 7 a.m. Thursday at Kaiser Permanente's Los Angeles Medical Center and at five Sutter corporation hospitals in Northern California.

The California Nurses Association says the RNs are calling on hospitals to increase staffing levels and take steps to retain experienced workers. They are also demanding policies that give RNs a stronger voice in patient care.

Officials say on Friday the strikers will be joined by nurses from Providence's Torrance hospital and Providence Saint John's Health Center in Santa Monica.

Hospital officials say backup workers will be used to make sure there is no interruption in care.